Disposable battery cells are utilized in a wide variety of applications to provide either a main source of power or back-up power to a wide variety of devices. These cells are typically acidic or alkaline electrolytic pastes contained in battery cans. The cans are fabricated from thin metal sheeting and then zinc and carbon or zinc and manganese oxide electrodes. The cans are typically manufactured as cylindrical shapes in standard sizes such as A, AA, AAA, C, D, etc. for well-known applications such as toys, flashlights, portable radios and the like. However, another cell shape known in the art as “prismatic” is enjoying increased usage for specialty applications, wherein the cell shape is non-cylindrical.
As an intermediate step in the manufacturing process of disposable battery cells, a graphite coating is applied to the interior of the battery can to form a uniform film on the interior of the base and sidewall up to a pre-selected height on the interior sidewall. Because the can is cylindrical, it has been the practice in the prior art of high volume manufacture of cylindrical battery cells to spin the empty battery cans lying horizontally on their sides at high speed while a graphite dispersion is applied via a spray gun and a nozzle inserted into the interior of the can. Non-cylindrical battery cans do not lend themselves to this method of applying graphite coatings, because they cannot be rotated around an axis at high speed as in the case of cylindrical battery cans.
While it would be possible to construct a special spray nozzle to conform to the interior of a prismatic battery can, this would require different sizes and shapes of spray nozzles. The application of a graphite coating in this manner would not be suitable for high speed, high volume production of battery cans.
Accordingly, one object of the present invention is to provide an improved process for applying a graphite coating to the interior of a non-cylindrical battery can.
Another object of the invention is to provide an improved process for applying graphite coatings to the interiors of a group of non-cylindrical battery cans moving continuously on a conveyor in a production line.